The city of Calgary is now proposing extending the tunnelled portion of the Green Line all the way from 24 Avenue North along Centre Street, to just before Inglewood Station inside the neighbourhood of Ramsay. This extension of the tunnel will bring the tunnelled portion of the line to around 1 km longer than previously proposed and will add 2 stations to the currently approved 4 subway stations. under this proposal, the subway will go under both of Calgary's major rivers, the Bow and Elbow. The tunnelled portion will be approximately 5.5 kilometres long with 6 stations if this newest proposed routing is approved. Ultimately, Calgary now has nearly 10 kilometres of subway proposed with 9 to 10 stations, with 5.5 km and 6 stations for the Green Line, and 4 km and 3 - 4 stations for the Red Line.

It's where insiders go and people with money. Apparently even Xi Jinping visits the site. He's probably checking to see what his citizens are buying and what's worth confiscating if times ever get real bad for the country.

Interlining can cause some operational difficulties. For example, if the vehicles are running at a very tight interval, even a small delay on one line could impact several lines. It's less of an issue for street-running vehicles like buses, streetcars or (to a lesser extent) LRT which tend to have shorter stopping distances and operate with less strict signalling requirements. But for something like a metro, it's difficult to interline without automation. In Montreal's case, automation is possible, but its proprietary technology would make it very costly.

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I've always struggled with reality. And I'm pleased to say that I won.

Interlining can cause some operational difficulties. For example, if the vehicles are running at a very tight interval, even a small delay on one line could impact several lines. It's less of an issue for street-running vehicles like buses, streetcars or (to a lesser extent) LRT which tend to have shorter stopping distances and operate with less strict signalling requirements. But for something like a metro, it's difficult to interline without automation. In Montreal's case, automation is possible, but its proprietary technology would make it very costly.

Interlining is common practice all over the world on every kind of passenger rail system. I am sure there are ways that problems are mitigated.

You're right and there are. However, it's just a bit more complicated in Montreal's case because of its proprietary trains and signalling. Whereas most cities can go for off-the-shelf solutions, Montreal would have to invent its own at a much greater cost.

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I've always struggled with reality. And I'm pleased to say that I won.

You're right and there are. However, it's just a bit more complicated in Montreal's case because of its proprietary trains and signalling. Whereas most cities can go for off-the-shelf solutions, Montreal would have to invent its own at a much greater cost.

The metro is already automated... just that the conductor needs to press a button to close doors. Interlining is good with low frequency trains (like the REM), but with a metro, stations can get full quick because people need to wait for THEIR train. If a transfer is easy and frequencies run high, independant lines are more operationnally efficient.

It's automated-ish. The main problem in having any meaningful automation is that currently the signalling currently can't tell where a train is other than to say that it is either at or between certain stations. That means that a train can't leave until the next one has left its station because if the one before it has to make an emergency stop between stations, it would get rammed at full speed. So frequency is limited to run time between the two furthest stations.

And then, as you rightly point out, there remains the issue of platform capacity which is already problematic at several stations.

So before any interlining can take place, the metro needs to be automated, which can't happen until all the tunnels, trains and command centres are outfitted with new, proprietary signalling. Then the busiest stations have to be re-excavated (since all metro stations are underground) to have their platforms widened to accommodate the increased congestion caused by people waiting.

So it's possible, but it'd just be very, very expensive. For the cost, you'd do better to just build parallel metro or LRT lines to alleviate the pressure.

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I've always struggled with reality. And I'm pleased to say that I won.

If trains run more frequently because of better signalling, does that not already address platform pressures?

No, the orange and blue lines are basically at operational capacities, green line and yellow lines would need more trains. The automation aspect is only part of it. There is the problematic of switching trains at the end of lines, plus tunnels in U shape, where for security reasons two trains can't be at the same time.

Even with the higher frequency, the plaftorms will still be half full and people will get in the way of people getting out. Interlining is fine for moderately sized systems. Interlining is usually removed when operational issues come into play. That is why, for example, you got Paris Line 3 and Line 3bis, where the main branch was way more popular then the other branch, and platorms were filling with people waiting for the lowest used branch. In Hong Kong, some branches are only interlined in non-rush hours.

If trains run more frequently because of better signalling, does that not already address platform pressures?

Say you have two stations:

Station A has a train every 90 seconds and only one line.
Station B also has a train every 90 seconds, but has two lines.

Station B will have more congestion than Station A because you'll have people getting in and out of the station plus people waiting on the platform for the next train. In Station A, the whole platform clears out every 90 seconds, but in B, you have people navigating their way around the waiting passengers.

So with interlining, you need wider platforms than you would otherwise need. It's definitely not an argument against interlining - it's just something that is necessary if ever you want to do it.

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I've always struggled with reality. And I'm pleased to say that I won.

Station A has a train every 90 seconds and only one line.
Station B also has a train every 90 seconds, but has two lines.

Station B will have more congestion than Station A because you'll have people getting in and out of the station plus people waiting on the platform for the next train. In Station A, the whole platform clears out every 90 seconds, but in B, you have people navigating their way around the waiting passengers.

So with interlining, you need wider platforms than you would otherwise need. It's definitely not an argument against interlining - it's just something that is necessary if ever you want to do it.

Assuming the same frequency, yes.

But the comment was made with the assumption that frequency could be improved significantly.

If that is the case, then it is possible to move more passengers through each station even with interlining. Yes, there would be more passengers on the platform than with a single line, but frequency would compensate for the accumulation of passengers on the platform.

Obviously, as you approach the line capacity, you can't continue to do that.

Also, depending on the degree of commonality of the interlined routes, many will be able to take the first train anyways reducing the platform problem.